/*
 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.util;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import sun.misc.SharedSecrets;

/**
 * Map接口的基于哈希表的实现。这个实现提供所有可选的map操作并允许
 * null值和null键。（HashMap该类大致等于Hashtable，除了它是不同步，并允许为null。）此类不保证
 * map的顺序；特别是不能保证顺序将随着时间的推移保持不变。
 * <p>
 * 此实现为基本功能提供时间常量的性能操作（get和put），假设使用哈希函数
 * 将元素适当地分散在桶中。迭代集合视图结束需要的时间与HashMap实例的“容量”（桶数）加上其大小（键值映射的数量）成正比。
 * 因此，重要的是如果迭代性能重要，不要设置过高的初始容量（或者加载因子过低）
 * 
 * <p>
 * 
 * HashMap的实例有两个参数会影响其性能：初始容量和加载因子。容量是哈希表中的桶数，容量只是创建哈希表时的容量。
 * 负载因子是衡量允许哈希表获取的满度的一种度量在自动增加容量之前。当哈希表中的entry数量超出了负载系数和当前容量，则哈希表被rehash
 * （即内部数据结构重建），以使哈希表具有大约两倍的桶数。
 * <p>
 * 
 * 通常，默认负载系数 （.75） 在时间和空间成本之间提供良好的权衡。
 * 值越高，空间开销越小，但查找成本增加（反映在HashMap类的大部分操作中，包括get和put）。
 * 在设置初始容量时，应考虑map中的预期entry数及其负载系数，以便尽量减少rehash操作的数量。
 * 如果初始容量大于最大entry数除以负载因子，则不会发生rehash操作。
 * <p>
 *
 * 如果要在HashMap实例中存储许多映射，创建具有足够大的容量允许存储映射比让它根据需要自动rehash来增长
 * 表更有效。请注意，使用多个具有相同{@code hashCode()}的键可以确保 降低任何哈希表性能的方法。
 * 为了改善影响，当键是Comparable，此类可以使用键之间的比较顺序 帮助打破关系。
 * <p>
 * 请注意，这个实现是不同步的。如果多线程并发的访问一个hashMap，并且至少一个线程修改map结构，它就必须外部同步。
 * （结构修改是添加或删除的任意操作一个或多个映射；仅仅修改一个key关联的value不是结构修改。）通常是通过自然地同步某个对象来完成封装map。
 *
 * 如果没有这样的对象存在，map应该用Collections.synchronizedMap方法包装。最好在创建的时候完成，预防意外的不同步使用map：
 * 
 * <pre>
 *   Map m = Collections.synchronizedMap(new HashMap(...));
 * </pre>
 *
 * <p>
 *
 * 此类的所有“集合视图方法”返回的迭代器均快速失败：如果在创建迭代器后的任何时间进行了结构修改，除了通过迭代器自己的 remove
 * 方法，迭代器将抛出{@link ConcurrentModificationException}。因此，面对并发修改，迭代器会快速干净地失败，而不会在未来的不确定时间内冒任何不确定的行为的风险。
 * 
 * <p>
 *
 * 请注意，迭代器的快速失败行为无法得到保证，一般来说，在存在非同步并发修改的情况下，不可能做出任何严格的保证。Fail-fast迭代器抛出
 * ConcurrentModificationException尽力而为。因此，编写依赖于此异常的程序是错误的
 * 正确性：迭代器的快速失败行为仅应用于检测错误。
 * <p>
 * This class is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> Java
 * Collections Framework</a>.
 *
 * @param <K> the type of keys maintained by this map
 * @param <V> the type of mapped values
 *
 * @author Doug Lea
 * @author Josh Bloch
 * @author Arthur van Hoff
 * @author Neal Gafter
 * @see Object#hashCode()
 * @see Collection
 * @see Map
 * @see TreeMap
 * @see Hashtable
 * @since 1.2
 */
public class HashMap<K, V> extends AbstractMap<K, V> implements Map<K, V>, Cloneable, Serializable {

    private static final long serialVersionUID = 362498820763181265L;

    /*
     * Implementation notes.
     *
     * This map usually acts as a binned (bucketed) hash table, but when bins get
     * too large, they are transformed into bins of TreeNodes, each structured
     * similarly to those in java.util.TreeMap. Most methods try to use normal bins,
     * but relay to TreeNode methods when applicable (simply by checking instanceof
     * a node). Bins of TreeNodes may be traversed and used like any others, but
     * additionally support faster lookup when overpopulated. However, since the
     * vast majority of bins in normal use are not overpopulated, checking for
     * existence of tree bins may be delayed in the course of table methods.
     *
     * 该映射通常用作装箱（桶）的哈希表，但是当箱被获取时
     * 太大，它们被转换成TreeNodes的bin，每个bined
     * 与java.util.TreeMap中的类似。大多数方法尝试使用普通垃圾箱
     * 但在适用时中继到TreeNode方法（只需通过检查instanceof
     * 一个节点）。 TreeNodes的bin可以像其他遍历一样遍历和使用，但是
     * 此外，在人口过多时还支持更快的查找。但是，由于
     * 正常使用中的绝大多数垃圾桶都没有人口过多，请检查
     * 在使用表方法的过程中，树箱的存在可能会延迟。
     * Tree bins (i.e., bins whose elements are all TreeNodes) are ordered primarily
     * by hashCode, but in the case of ties, if two elements are of the same
     * "class C implements Comparable<C>", type then their compareTo method is used
     * for ordering. (We conservatively check generic types via reflection to
     * validate this -- see method comparableClassFor). The added complexity of tree
     * bins is worthwhile in providing worst-case O(log n) operations when keys
     * either have distinct hashes or are orderable, Thus, performance degrades
     * gracefully under accidental or malicious usages in which hashCode() methods
     * return values that are poorly distributed, as well as those in which many
     * keys share a hashCode, so long as they are also Comparable. (If neither of
     * these apply, we may waste about a factor of two in time and space compared to
     * taking no precautions. But the only known cases stem from poor user
     * programming practices that are already so slow that this makes little
     * difference.)
     *
     * Because TreeNodes are about twice the size of regular nodes, we use them only
     * when bins contain enough nodes to warrant use (see TREEIFY_THRESHOLD). And
     * when they become too small (due to removal or resizing) they are converted
     * back to plain bins. In usages with well-distributed user hashCodes, tree bins
     * are rarely used. Ideally, under random hashCodes, the frequency of nodes in
     * bins follows a Poisson distribution
     * (http://en.wikipedia.org/wiki/Poisson_distribution) with a parameter of about
     * 0.5 on average for the default resizing threshold of 0.75, although with a
     * large variance because of resizing granularity. Ignoring variance, the
     * expected occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
     * factorial(k)). The first values are:
     *
     * 0: 0.60653066 1: 0.30326533 2: 0.07581633 3: 0.01263606 4: 0.00157952 5:
     * 0.00015795 6: 0.00001316 7: 0.00000094 8: 0.00000006 more: less than 1 in ten
     * million
     *
     * The root of a tree bin is normally its first node. However, sometimes
     * (currently only upon Iterator.remove), the root might be elsewhere, but can
     * be recovered following parent links (method TreeNode.root()).
     *
     * All applicable internal methods accept a hash code as an argument (as
     * normally supplied from a public method), allowing them to call each other
     * without recomputing user hashCodes. Most internal methods also accept a "tab"
     * argument, that is normally the current table, but may be a new or old one
     * when resizing or converting.
     *
     * When bin lists are treeified, split, or untreeified, we keep them in the same
     * relative access/traversal order (i.e., field Node.next) to better preserve
     * locality, and to slightly simplify handling of splits and traversals that
     * invoke iterator.remove. When using comparators on insertion, to keep a total
     * ordering (or as close as is required here) across rebalancings, we compare
     * classes and identityHashCodes as tie-breakers.
     *
     * The use and transitions among plain vs tree modes is complicated by the
     * existence of subclass LinkedHashMap. See below for hook methods defined to be
     * invoked upon insertion, removal and access that allow LinkedHashMap internals
     * to otherwise remain independent of these mechanics. (This also requires that
     * a map instance be passed to some utility methods that may create new nodes.)
     *
     * The concurrent-programming-like SSA-based coding style helps avoid aliasing
     * errors amid all of the twisty pointer operations.
     */

    /**
     * 默认初始容量16 必须为2的幂
     */
    static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16

    /**
     * The maximum capacity, used if a higher value is implicitly specified by
     * either of the constructors with arguments. MUST be a power of two <= 1<<30.
     * 最大容量，2的30次方
     */
    static final int MAXIMUM_CAPACITY = 1 << 30;

    /**
     * 默认负载因子在构造函数未指定时使用
     */
    static final float DEFAULT_LOAD_FACTOR = 0.75f;

    /**
     * The bin count threshold for using a tree rather than list for a bin. Bins are
     * converted to trees when adding an element to a bin with at least this many
     * nodes. The value must be greater than 2 and should be at least 8 to mesh with
     * assumptions in tree removal about conversion back to plain bins upon
     * shrinkage.
     * 使用树而不是list的bin数阈值。当添加元素到bin至少8个nodes bin转换成tree
     * 数值必须大于2并且至少为8，在tree删除转化为普通bins
     * 
     */
    static final int TREEIFY_THRESHOLD = 8;

    /**
     * The bin count threshold for untreeifying a (split) bin during a resize
     * operation. Should be less than TREEIFY_THRESHOLD, and at most 6 to mesh with
     * shrinkage detection under removal.
     * 当调整大小的时候bin取消树（拆分）的bin数阈值。应该小于TREEIFY_THRESHOLD，并且大于6
     */
    static final int UNTREEIFY_THRESHOLD = 6;

    /**
     * The smallest table capacity for which bins may be treeified. (Otherwise the
     * table is resized if too many nodes in a bin.) Should be at least 4 *
     * TREEIFY_THRESHOLD to avoid conflicts between resizing and treeification
     * thresholds. 
     * 树形化最小表容量。（否则，如果一个bin中有太多节点，就会重新调整表的大小。）应该至少4*TREEIFY_THRESHOLD
     * 去避免调整大小并且树形化的阈值
     * 
     */
    static final int MIN_TREEIFY_CAPACITY = 64;

    /**
     * Basic hash bin node, used for most entries. (See below for TreeNode subclass,
     * and in LinkedHashMap for its Entry subclass.)
     * 
     */
    static class Node<K, V> implements Map.Entry<K, V> {
        final int hash;
        final K key;
        V value;
        Node<K, V> next;

        Node(int hash, K key, V value, Node<K, V> next) {
            this.hash = hash;
            this.key = key;
            this.value = value;
            this.next = next;
        }

        public final K getKey() {
            return key;
        }

        public final V getValue() {
            return value;
        }

        public final String toString() {
            return key + "=" + value;
        }

        public final int hashCode() {
            return Objects.hashCode(key) ^ Objects.hashCode(value);
        }

        public final V setValue(V newValue) {
            V oldValue = value;
            value = newValue;
            return oldValue;
        }

        public final boolean equals(Object o) {
            if (o == this)
                return true;
            if (o instanceof Map.Entry) {
                Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
                if (Objects.equals(key, e.getKey()) && Objects.equals(value, e.getValue()))
                    return true;
            }
            return false;
        }
    }

    /* ---------------- Static utilities -------------- */

    /**
     * Computes key.hashCode() and spreads (XORs) higher bits of hash to lower.
     * Because the table uses power-of-two masking, sets of hashes that vary only in
     * bits above the current mask will always collide. (Among known examples are
     * sets of Float keys holding consecutive whole numbers in small tables.) So we
     * apply a transform that spreads the impact of higher bits downward. There is a
     * tradeoff between speed, utility, and quality of bit-spreading. Because many
     * common sets of hashes are already reasonably distributed (so don't benefit
     * from spreading), and because we use trees to handle large sets of collisions
     * in bins, we just XOR some shifted bits in the cheapest possible way to reduce
     * systematic lossage, as well as to incorporate impact of the highest bits that
     * would otherwise never be used in index calculations because of table bounds.
     * 
     * &与 都为1 结果为1否则为0
     * |或 只要一个为1 结果为1否则为0
     * ～非 为1结果为0 为0结果为1
     * ^ 异或 相同为0 不同为1
     *
     * 计算key.hashCode()并将哈希的较高位扩展（异或）到较低位。
     * 由于该表使用2的幂次掩码，因此仅在当前掩码上方的位中变化的哈希集将始终发生冲突。 （众所周知的示例是在小表中保存连续整数的Float键集。）因此，我们应用了一种变换，将向下传播较高位的影响。在速度，实用性和位扩展质量之间需要权衡。由于许多常见的哈希集已经合理分布（因此无法从扩展中受益），并且由于我们使用树来处理容器中的大量冲突集，因此我们仅以最便宜的方式对某些移位后的位进行XOR，以减少系统损失，以及合并最高位的影响，否则由于表范围的限制，这些位将永远不会在索引计算中使用。
     * 
     * hashcode低16位与高16位异或 更加散列
     */
    static final int hash(Object key) {
        int h;
        return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
    }

    /**
     * Returns x's Class if it is of the form "class C implements Comparable<C>",
     * else null.
     */
    static Class<?> comparableClassFor(Object x) {
        if (x instanceof Comparable) {
            Class<?> c;
            Type[] ts, as;
            Type t;
            ParameterizedType p;
            if ((c = x.getClass()) == String.class) // bypass checks
                return c;
            if ((ts = c.getGenericInterfaces()) != null) {
                for (int i = 0; i < ts.length; ++i) {
                    if (((t = ts[i]) instanceof ParameterizedType)
                            && ((p = (ParameterizedType) t).getRawType() == Comparable.class)
                            && (as = p.getActualTypeArguments()) != null && as.length == 1 && as[0] == c) // type arg is
                                                                                                          // c
                        return c;
                }
            }
        }
        return null;
    }

    /**
     * Returns k.compareTo(x) if x matches kc (k's screened comparable class), else
     * 0.
     */
    @SuppressWarnings({ "rawtypes", "unchecked" }) // for cast to Comparable
    static int compareComparables(Class<?> kc, Object k, Object x) {
        return (x == null || x.getClass() != kc ? 0 : ((Comparable) k).compareTo(x));
    }

    /**
     * Returns a power of two size for the given target capacity.
     * 返回一个2的幂 大于等于容量
     */
    static final int tableSizeFor(int cap) {
        //经过下面的 或 和位移 运算， n最终各位都是1。
        int n = cap - 1;
        n |= n >>> 1;
        n |= n >>> 2;
        n |= n >>> 4;
        n |= n >>> 8;
        n |= n >>> 16;
        //判断n是否越界，返回 2的n次方作为 table（哈希桶）的阈值
        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
    }

    /* ---------------- Fields -------------- */

    /**
     * The table, initialized on first use, and resized as necessary. When
     * allocated, length is always a power of two. (We also tolerate length zero in
     * some operations to allow bootstrapping mechanics that are currently not
     * needed.) 
     * 该表在首次使用时初始化，并根据需要调整大小。分配后，长度始终是2的幂。
     * （在某些操作中，我们还允许长度为零，以允许使用当前不需要的引导机制。）
     * 
     */
    transient Node<K, V>[] table;

    /**
     * Holds cached entrySet(). Note that AbstractMap fields are used for keySet()
     * and values().
     */
    transient Set<Map.Entry<K, V>> entrySet;

    /**
     * The number of key-value mappings contained in this map.
     */
    transient int size;

    /**
     * The number of times this HashMap has been structurally modified Structural
     * modifications are those that change the number of mappings in the HashMap or
     * otherwise modify its internal structure (e.g., rehash). This field is used to
     * make iterators on Collection-views of the HashMap fail-fast. (See
     * ConcurrentModificationException).
     */
    transient int modCount;

    /**
     * The next size value at which to resize (capacity * load factor).
     * 下一个调整大小的值（容量*负载因子） 。
     * 另外，如果表数组没有分配，这个属性保存初始数组容量，或者为0表示DEFAULT_INITIAL_CAPACITY
     * 
     * @serial
     */
    // (The javadoc description is true upon serialization.
    // Additionally, if the table array has not been allocated, this
    // field holds the initial array capacity, or zero signifying
    // DEFAULT_INITIAL_CAPACITY.)
    int threshold;

    /**
     * The load factor for the hash table.
     *
     * @serial
     */
    final float loadFactor;

    /* ---------------- Public operations -------------- */

    /**
     * Constructs an empty <tt>HashMap</tt> with the specified initial capacity and
     * load factor.
     *
     * @param initialCapacity the initial capacity
     * @param loadFactor      the load factor
     * @throws IllegalArgumentException if the initial capacity is negative or the
     *                                  load factor is nonpositive
     */
    public HashMap(int initialCapacity, float loadFactor) {
        // 边界处理
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal initial capacity: " + initialCapacity);
        // 初始容量不能大于2的30次方
        if (initialCapacity > MAXIMUM_CAPACITY)
            initialCapacity = MAXIMUM_CAPACITY;
        // 负载因子不能为负数
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new IllegalArgumentException("Illegal load factor: " + loadFactor);
        this.loadFactor = loadFactor;
        //设置阈值为 》=初始化容量的 2的n次方的值
        this.threshold = tableSizeFor(initialCapacity);
    }

    /**
     * 使用指定初始化容量和默认负载因子（0.75f）创建一个空HashMap
     * @param initialCapacity the initial capacity.
     * @throws IllegalArgumentException if the initial capacity is negative.
     */
    public HashMap(int initialCapacity) {
        //指定初始化容量的构造函数
        this(initialCapacity, DEFAULT_LOAD_FACTOR);
    }

    /**
     * Constructs an empty <tt>HashMap</tt> with the default initial capacity (16)
     * and the default load factor (0.75).
     * 
     */
    public HashMap() {
        //默认构造函数，赋值加载因子为默认的0.75f
        this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
    }

    /**
     * Constructs a new <tt>HashMap</tt> with the same mappings as the specified
     * <tt>Map</tt>. The <tt>HashMap</tt> is created with default load factor (0.75)
     * and an initial capacity sufficient to hold the mappings in the specified
     * <tt>Map</tt>.
     *
     * //新建一个哈希表，同时将另一个map m 里的所有元素加入表中
     * @param m the map whose mappings are to be placed in this map
     * @throws NullPointerException if the specified map is null
     */
    public HashMap(Map<? extends K, ? extends V> m) {
        this.loadFactor = DEFAULT_LOAD_FACTOR;
        putMapEntries(m, false);
    }

    /**
     * Implements Map.putAll and Map constructor.
     *
     * @param m     the map
     * @param evict false when initially constructing this map, else true (relayed
     *              to method afterNodeInsertion).
     */
    //将另一个Map的所有元素加入表中，参数evict初始化时为false，其他情况为true
    final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
        //拿到m的元素数量
        int s = m.size();
        //如果数量大于0
        if (s > 0) {
            //如果当前表是空的
            if (table == null) { // pre-size
                //根据m的元素数量和当前表的加载因子，计算出阈值
                float ft = ((float) s / loadFactor) + 1.0F;
                //修正阈值的边界 不能超过MAXIMUM_CAPACITY
                int t = ((ft < (float) MAXIMUM_CAPACITY) ? (int) ft : MAXIMUM_CAPACITY);
                //如果新的阈值大于当前阈值
                if (t > threshold)
                    //返回一个 》=新的阈值的 满足2的n次方的阈值
                    threshold = tableSizeFor(t);
                //如果当前元素表不是空的，但是 m的元素数量大于阈值，说明一定要扩容。
            } else if (s > threshold)
                resize();
            //遍历 m 依次将元素加入当前表中。
            for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
                K key = e.getKey();
                V value = e.getValue();
                putVal(hash(key), key, value, false, evict);
            }
        }
    }

    /**
     * Returns the number of key-value mappings in this map.
     *
     * @return the number of key-value mappings in this map
     */
    public int size() {
        return size;
    }

    /**
     * Returns <tt>true</tt> if this map contains no key-value mappings.
     *
     * @return <tt>true</tt> if this map contains no key-value mappings
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * Returns the value to which the specified key is mapped, or {@code null} if
     * this map contains no mapping for the key.
     *
     * <p>
     * More formally, if this map contains a mapping from a key {@code k} to a value
     * {@code v} such that {@code (key==null ? k==null :
     * key.equals(k))}, then this method returns {@code v}; otherwise it returns
     * {@code null}. (There can be at most one such mapping.)
     *
     * <p>
     * A return value of {@code null} does not <i>necessarily</i> indicate that the
     * map contains no mapping for the key; it's also possible that the map
     * explicitly maps the key to {@code null}. The {@link #containsKey containsKey}
     * operation may be used to distinguish these two cases.
     *
     * @see #put(Object, Object)
     */
    public V get(Object key) {
        Node<K, V> e;
        return (e = getNode(hash(key), key)) == null ? null : e.value;
    }

    /**
     * Implements Map.get and related methods.
     *
     * @param hash hash for key
     * @param key  the key
     * @return the node, or null if none
     */
    final Node<K, V> getNode(int hash, Object key) {
        Node<K, V>[] tab;
        Node<K, V> first, e;
        int n;
        K k;
        if ((tab = table) != null && (n = tab.length) > 0 && (first = tab[(n - 1) & hash]) != null) {
            if (first.hash == hash && // always check first node
                    ((k = first.key) == key || (key != null && key.equals(k))))
                return first;
            if ((e = first.next) != null) {
                if (first instanceof TreeNode)
                    return ((TreeNode<K, V>) first).getTreeNode(hash, key);
                do {
                    if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k))))
                        return e;
                } while ((e = e.next) != null);
            }
        }
        return null;
    }

    /**
     * Returns <tt>true</tt> if this map contains a mapping for the specified key.
     *
     * @param key The key whose presence in this map is to be tested
     * @return <tt>true</tt> if this map contains a mapping for the specified key.
     */
    public boolean containsKey(Object key) {
        return getNode(hash(key), key) != null;
    }

    /**
     * Associates the specified value with the specified key in this map. If the map
     * previously contained a mapping for the key, the old value is replaced.
     *
     * @param key   key with which the specified value is to be associated
     * @param value value to be associated with the specified key
     * @return the previous value associated with <tt>key</tt>, or <tt>null</tt> if
     *         there was no mapping for <tt>key</tt>. (A <tt>null</tt> return can
     *         also indicate that the map previously associated <tt>null</tt> with
     *         <tt>key</tt>.)
     */
    public V put(K key, V value) {
        return putVal(hash(key), key, value, false, true);
    }

    /**
     * Implements Map.put and related methods.
     *
     * @param hash         hash for key
     * @param key          the key
     * @param value        the value to put
     * @param onlyIfAbsent if true, don't change existing value
     * @param evict        if false, the table is in creation mode.
     * @return previous value, or null if none
     */
    final V putVal(int hash, K key, V value, boolean onlyIfAbsent, boolean evict) {
        //tab存放 当前的哈希桶， p用作临时链表节点
        Node<K, V>[] tab;
        Node<K, V> p;
        int n, i;
        //如果当前哈希表是空的，代表是初始化
        if ((tab = table) == null || (n = tab.length) == 0)
            //那么直接去扩容哈希表，并且将扩容后的哈希桶长度赋值给n
            n = (tab = resize()).length;
        //如果当前index的节点是空的，表示没有发生哈希碰撞。 直接构建一个新节点Node，挂载在index处即可。
        //index 是利用 哈希值 & 哈希桶的长度-1，替代模运算
        if ((p = tab[i = (n - 1) & hash]) == null)
            tab[i] = newNode(hash, key, value, null);
        else {//否则 发生了哈希冲突。
            Node<K, V> e;
            K k;
            //如果哈希值相等，key也相等，则是覆盖value操作
            if (p.hash == hash && ((k = p.key) == key || (key != null && key.equals(k))))
                e = p;//将当前节点引用赋值给e
            else if (p instanceof TreeNode)
                e = ((TreeNode<K, V>) p).putTreeVal(this, tab, hash, key, value);
            else {
                for (int binCount = 0;; ++binCount) {
                    if ((e = p.next) == null) {
                        p.next = newNode(hash, key, value, null);
                        if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
                            treeifyBin(tab, hash);
                        break;
                    }
                    if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k))))
                        break;
                    p = e;
                }
            }
            if (e != null) { // existing mapping for key
                V oldValue = e.value;
                if (!onlyIfAbsent || oldValue == null)
                    e.value = value;
                afterNodeAccess(e);
                return oldValue;
            }
        }
        ++modCount;
        if (++size > threshold)
            resize();
        afterNodeInsertion(evict);
        return null;
    }

    /**
     * Initializes or doubles table size. If null, allocates in accord with initial
     * capacity target held in field threshold. Otherwise, because we are using
     * power-of-two expansion, the elements from each bin must either stay at same
     * index, or move with a power of two offset in the new table.
     * 初始化或者双倍表的大小。如果null，在属性阈值的约束下分配符合初始容量目标，因为我们用2的幂扩大，或者在新的表中用2的幂偏移量移动
     * @return the table
     */
    final Node<K, V>[] resize() {
        //oldTab 为当前表的哈希桶
        Node<K, V>[] oldTab = table;
        //当前哈希桶的容量 length
        int oldCap = (oldTab == null) ? 0 : oldTab.length;
        // 当前阈值
        int oldThr = threshold;
        //初始化新的容量和阈值为0
        int newCap, newThr = 0;
        //如果当前容量大于0
        if (oldCap > 0) {
            //如果当前容量已经到达上限
            if (oldCap >= MAXIMUM_CAPACITY) {
                //则设置阈值是2的31次方-1（防止翻倍后容量超过Integer的最大容量）
                threshold = Integer.MAX_VALUE;
                //同时返回当前的哈希桶，不再扩容
                return oldTab;
            //否则新的容量为旧的容量的两倍。
            } else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY && oldCap >= DEFAULT_INITIAL_CAPACITY) //如果旧的容量大于等于默认初始容量16
                //那么新的阈值也等于旧的阈值的两倍
                newThr = oldThr << 1; // double threshold
        //如果当前表是空的，但是有阈值。代表是初始化时指定了容量、阈值的情况
        } else if (oldThr > 0) // initial capacity was placed in threshold
            // 那么新表的容量就等于旧的阈值
            newCap = oldThr;
        //如果当前表是空的，而且也没有阈值。代表是初始化时没有任何容量/阈值参数的情况
        else { // zero initial threshold signifies using defaults
            newCap = DEFAULT_INITIAL_CAPACITY;  //此时新表的容量为默认的容量 16

            newThr = (int) (DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);    // 新阈值为默认负载因子(16)*默认初始容量(0.75f) = 12
        }
        //如果新的阈值是0，对应的是 当前表是空的，但是有阈值的情况
        if (newThr == 0) {
            float ft = (float) newCap * loadFactor;     //根据新表容量 和 加载因子 求出新的阈值
            //进行越界修复
            newThr = (newCap < MAXIMUM_CAPACITY && ft < (float) MAXIMUM_CAPACITY ? (int) ft : Integer.MAX_VALUE);
        }
        //更新阈值
        threshold = newThr;
        @SuppressWarnings({ "rawtypes", "unchecked" })
        //根据新的容量 构建新的哈希桶
        Node<K, V>[] newTab = (Node<K, V>[]) new Node[newCap];
        //更新哈希桶引用
        table = newTab;
        //如果以前的哈希桶中有元素
        //下面开始将当前哈希桶中的所有节点转移到新的哈希桶中
        if (oldTab != null) {
            //遍历老的哈希桶
            for (int j = 0; j < oldCap; ++j) {
                //取出当前的节点 e
                Node<K, V> e;
                //如果当前桶中有元素,则将链表赋值给e
                if ((e = oldTab[j]) != null) {
                    //将原哈希桶置空以便GC
                    oldTab[j] = null;
                    //如果当前链表中就一个元素，（没有发生哈希碰撞）
                    if (e.next == null)
                        //直接将这个元素放置在新的哈希桶里。
                        //注意这里取下标 是用 哈希值 与 桶的长度-1 。 由于桶的长度是2的n次方，这么做其 实是等于 一个模运算。但是效率更高
                        newTab[e.hash & (newCap - 1)] = e;
                    //如果发生过哈希碰撞 ,而且是节点数超过8个，转化成了红黑树
                    else if (e instanceof TreeNode)
                        ((TreeNode<K, V>) e).split(this, newTab, j, oldCap);
                    //如果发生过哈希碰撞，节点数小于8个。则要根据链表上每个节点的哈希值，依次放入新哈希 桶对应下标位置。
                    else { // preserve order
                        //因为扩容是容量翻倍，所以原链表上的每个节点，现在可能存放在原来的下标，即low 位， 或者扩容后的下标，即high位。 high位= low位+原哈希桶容量
                        //低位链表的头结点、尾节点
                        Node<K, V> loHead = null, loTail = null;
                        //高位链表的头节点、尾节点
                        Node<K, V> hiHead = null, hiTail = null;
                        Node<K, V> next;//临时节点 存放e的下一个节点
                        do {
                            next = e.next;
                            //这里又是一个利用位运算代替常规运算的高效点：利用哈希值 与 旧的容量，可以得到哈希值去模后，是大于等于oldCap还是小于oldCap，等于0代表小于oldCap，应该存放在低位，否则存放在高位
                            //  oldCap
                            //         010000 & 010001 > 0
                            //         010000 & 001001 == 0
                            if ((e.hash & oldCap) == 0) {
                                //给头尾节点指针赋值
                                if (loTail == null)
                                    loHead = e;
                                else
                                    loTail.next = e;
                                loTail = e;
                            } else {//高位也是相同的逻辑
                                if (hiTail == null)
                                    hiHead = e;
                                else
                                    hiTail.next = e;
                                hiTail = e;
                            }
                        } while ((e = next) != null);//循环直到链表结束
                        //将低位链表存放在原index处，
                        if (loTail != null) {
                            loTail.next = null;
                            newTab[j] = loHead;
                        }
                        //将高位链表存放在新index处
                        if (hiTail != null) {
                            hiTail.next = null;
                            newTab[j + oldCap] = hiHead;
                        }
                    }
                }
            }
        }
        return newTab;
    }

    /**
     * Replaces all linked nodes in bin at index for given hash unless table is too
     * small, in which case resizes instead.
     */
    final void treeifyBin(Node<K, V>[] tab, int hash) {
        int n, index;
        Node<K, V> e;
        if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
            resize();
        else if ((e = tab[index = (n - 1) & hash]) != null) {
            TreeNode<K, V> hd = null, tl = null;
            do {
                TreeNode<K, V> p = replacementTreeNode(e, null);
                if (tl == null)
                    hd = p;
                else {
                    p.prev = tl;
                    tl.next = p;
                }
                tl = p;
            } while ((e = e.next) != null);
            if ((tab[index] = hd) != null)
                hd.treeify(tab);
        }
    }

    /**
     * Copies all of the mappings from the specified map to this map. These mappings
     * will replace any mappings that this map had for any of the keys currently in
     * the specified map.
     *
     * @param m mappings to be stored in this map
     * @throws NullPointerException if the specified map is null
     */
    public void putAll(Map<? extends K, ? extends V> m) {
        putMapEntries(m, true);
    }

    /**
     * Removes the mapping for the specified key from this map if present.
     *
     * @param key key whose mapping is to be removed from the map
     * @return the previous value associated with <tt>key</tt>, or <tt>null</tt> if
     *         there was no mapping for <tt>key</tt>. (A <tt>null</tt> return can
     *         also indicate that the map previously associated <tt>null</tt> with
     *         <tt>key</tt>.)
     */
    public V remove(Object key) {
        Node<K, V> e;
        return (e = removeNode(hash(key), key, null, false, true)) == null ? null : e.value;
    }

    /**
     * Implements Map.remove and related methods.
     *
     * @param hash       hash for key
     * @param key        the key
     * @param value      the value to match if matchValue, else ignored
     * @param matchValue if true only remove if value is equal
     * @param movable    if false do not move other nodes while removing
     * @return the node, or null if none
     */
    final Node<K, V> removeNode(int hash, Object key, Object value, boolean matchValue, boolean movable) {
        Node<K, V>[] tab;
        Node<K, V> p;
        int n, index;
        if ((tab = table) != null && (n = tab.length) > 0 && (p = tab[index = (n - 1) & hash]) != null) {
            Node<K, V> node = null, e;
            K k;
            V v;
            if (p.hash == hash && ((k = p.key) == key || (key != null && key.equals(k))))
                node = p;
            else if ((e = p.next) != null) {
                if (p instanceof TreeNode)
                    node = ((TreeNode<K, V>) p).getTreeNode(hash, key);
                else {
                    do {
                        if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
                            node = e;
                            break;
                        }
                        p = e;
                    } while ((e = e.next) != null);
                }
            }
            if (node != null && (!matchValue || (v = node.value) == value || (value != null && value.equals(v)))) {
                if (node instanceof TreeNode)
                    ((TreeNode<K, V>) node).removeTreeNode(this, tab, movable);
                else if (node == p)
                    tab[index] = node.next;
                else
                    p.next = node.next;
                ++modCount;
                --size;
                afterNodeRemoval(node);
                return node;
            }
        }
        return null;
    }

    /**
     * Removes all of the mappings from this map. The map will be empty after this
     * call returns.
     */
    public void clear() {
        Node<K, V>[] tab;
        modCount++;
        if ((tab = table) != null && size > 0) {
            size = 0;
            for (int i = 0; i < tab.length; ++i)
                tab[i] = null;
        }
    }

    /**
     * Returns <tt>true</tt> if this map maps one or more keys to the specified
     * value.
     *
     * @param value value whose presence in this map is to be tested
     * @return <tt>true</tt> if this map maps one or more keys to the specified
     *         value
     */
    public boolean containsValue(Object value) {
        Node<K, V>[] tab;
        V v;
        if ((tab = table) != null && size > 0) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K, V> e = tab[i]; e != null; e = e.next) {
                    if ((v = e.value) == value || (value != null && value.equals(v)))
                        return true;
                }
            }
        }
        return false;
    }

    /**
     * Returns a {@link Set} view of the keys contained in this map. The set is
     * backed by the map, so changes to the map are reflected in the set, and
     * vice-versa. If the map is modified while an iteration over the set is in
     * progress (except through the iterator's own <tt>remove</tt> operation), the
     * results of the iteration are undefined. The set supports element removal,
     * which removes the corresponding mapping from the map, via the
     * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
     * <tt>retainAll</tt>, and <tt>clear</tt> operations. It does not support the
     * <tt>add</tt> or <tt>addAll</tt> operations.
     *
     * @return a set view of the keys contained in this map
     */
    public Set<K> keySet() {
        Set<K> ks = keySet;
        if (ks == null) {
            ks = new KeySet();
            keySet = ks;
        }
        return ks;
    }

    final class KeySet extends AbstractSet<K> {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator<K> iterator() {
            return new KeyIterator();
        }

        public final boolean contains(Object o) {
            return containsKey(o);
        }

        public final boolean remove(Object key) {
            return removeNode(hash(key), key, null, false, true) != null;
        }

        public final Spliterator<K> spliterator() {
            return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer<? super K> action) {
            Node<K, V>[] tab;
            if (action == null)
                throw new NullPointerException();
            if (size > 0 && (tab = table) != null) {
                int mc = modCount;
                for (int i = 0; i < tab.length; ++i) {
                    for (Node<K, V> e = tab[i]; e != null; e = e.next)
                        action.accept(e.key);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    /**
     * Returns a {@link Collection} view of the values contained in this map. The
     * collection is backed by the map, so changes to the map are reflected in the
     * collection, and vice-versa. If the map is modified while an iteration over
     * the collection is in progress (except through the iterator's own
     * <tt>remove</tt> operation), the results of the iteration are undefined. The
     * collection supports element removal, which removes the corresponding mapping
     * from the map, via the <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
     * <tt>removeAll</tt>, <tt>retainAll</tt> and <tt>clear</tt> operations. It does
     * not support the <tt>add</tt> or <tt>addAll</tt> operations.
     *
     * @return a view of the values contained in this map
     */
    public Collection<V> values() {
        Collection<V> vs = values;
        if (vs == null) {
            vs = new Values();
            values = vs;
        }
        return vs;
    }

    final class Values extends AbstractCollection<V> {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator<V> iterator() {
            return new ValueIterator();
        }

        public final boolean contains(Object o) {
            return containsValue(o);
        }

        public final Spliterator<V> spliterator() {
            return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer<? super V> action) {
            Node<K, V>[] tab;
            if (action == null)
                throw new NullPointerException();
            if (size > 0 && (tab = table) != null) {
                int mc = modCount;
                for (int i = 0; i < tab.length; ++i) {
                    for (Node<K, V> e = tab[i]; e != null; e = e.next)
                        action.accept(e.value);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    /**
     * Returns a {@link Set} view of the mappings contained in this map. The set is
     * backed by the map, so changes to the map are reflected in the set, and
     * vice-versa. If the map is modified while an iteration over the set is in
     * progress (except through the iterator's own <tt>remove</tt> operation, or
     * through the <tt>setValue</tt> operation on a map entry returned by the
     * iterator) the results of the iteration are undefined. The set supports
     * element removal, which removes the corresponding mapping from the map, via
     * the <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, <tt>removeAll</tt>,
     * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not support the
     * <tt>add</tt> or <tt>addAll</tt> operations.
     *
     * @return a set view of the mappings contained in this map
     */
    public Set<Map.Entry<K, V>> entrySet() {
        Set<Map.Entry<K, V>> es;
        return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
    }

    final class EntrySet extends AbstractSet<Map.Entry<K, V>> {
        public final int size() {
            return size;
        }

        public final void clear() {
            HashMap.this.clear();
        }

        public final Iterator<Map.Entry<K, V>> iterator() {
            return new EntryIterator();
        }

        public final boolean contains(Object o) {
            if (!(o instanceof Map.Entry))
                return false;
            Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
            Object key = e.getKey();
            Node<K, V> candidate = getNode(hash(key), key);
            return candidate != null && candidate.equals(e);
        }

        public final boolean remove(Object o) {
            if (o instanceof Map.Entry) {
                Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
                Object key = e.getKey();
                Object value = e.getValue();
                return removeNode(hash(key), key, value, true, true) != null;
            }
            return false;
        }

        public final Spliterator<Map.Entry<K, V>> spliterator() {
            return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
        }

        public final void forEach(Consumer<? super Map.Entry<K, V>> action) {
            Node<K, V>[] tab;
            if (action == null)
                throw new NullPointerException();
            if (size > 0 && (tab = table) != null) {
                int mc = modCount;
                for (int i = 0; i < tab.length; ++i) {
                    for (Node<K, V> e = tab[i]; e != null; e = e.next)
                        action.accept(e);
                }
                if (modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }
    }

    // Overrides of JDK8 Map extension methods

    @Override
    public V getOrDefault(Object key, V defaultValue) {
        Node<K, V> e;
        return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
    }

    @Override
    public V putIfAbsent(K key, V value) {
        return putVal(hash(key), key, value, true, true);
    }

    @Override
    public boolean remove(Object key, Object value) {
        return removeNode(hash(key), key, value, true, true) != null;
    }

    @Override
    public boolean replace(K key, V oldValue, V newValue) {
        Node<K, V> e;
        V v;
        if ((e = getNode(hash(key), key)) != null && ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
            e.value = newValue;
            afterNodeAccess(e);
            return true;
        }
        return false;
    }

    @Override
    public V replace(K key, V value) {
        Node<K, V> e;
        if ((e = getNode(hash(key), key)) != null) {
            V oldValue = e.value;
            e.value = value;
            afterNodeAccess(e);
            return oldValue;
        }
        return null;
    }

    @Override
    public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
        if (mappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node<K, V>[] tab;
        Node<K, V> first;
        int n, i;
        int binCount = 0;
        TreeNode<K, V> t = null;
        Node<K, V> old = null;
        if (size > threshold || (tab = table) == null || (n = tab.length) == 0)
            n = (tab = resize()).length;
        if ((first = tab[i = (n - 1) & hash]) != null) {
            if (first instanceof TreeNode)
                old = (t = (TreeNode<K, V>) first).getTreeNode(hash, key);
            else {
                Node<K, V> e = first;
                K k;
                do {
                    if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
                        old = e;
                        break;
                    }
                    ++binCount;
                } while ((e = e.next) != null);
            }
            V oldValue;
            if (old != null && (oldValue = old.value) != null) {
                afterNodeAccess(old);
                return oldValue;
            }
        }
        V v = mappingFunction.apply(key);
        if (v == null) {
            return null;
        } else if (old != null) {
            old.value = v;
            afterNodeAccess(old);
            return v;
        } else if (t != null)
            t.putTreeVal(this, tab, hash, key, v);
        else {
            tab[i] = newNode(hash, key, v, first);
            if (binCount >= TREEIFY_THRESHOLD - 1)
                treeifyBin(tab, hash);
        }
        ++modCount;
        ++size;
        afterNodeInsertion(true);
        return v;
    }

    public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        if (remappingFunction == null)
            throw new NullPointerException();
        Node<K, V> e;
        V oldValue;
        int hash = hash(key);
        if ((e = getNode(hash, key)) != null && (oldValue = e.value) != null) {
            V v = remappingFunction.apply(key, oldValue);
            if (v != null) {
                e.value = v;
                afterNodeAccess(e);
                return v;
            } else
                removeNode(hash, key, null, false, true);
        }
        return null;
    }

    @Override
    public V compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        if (remappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node<K, V>[] tab;
        Node<K, V> first;
        int n, i;
        int binCount = 0;
        TreeNode<K, V> t = null;
        Node<K, V> old = null;
        if (size > threshold || (tab = table) == null || (n = tab.length) == 0)
            n = (tab = resize()).length;
        if ((first = tab[i = (n - 1) & hash]) != null) {
            if (first instanceof TreeNode)
                old = (t = (TreeNode<K, V>) first).getTreeNode(hash, key);
            else {
                Node<K, V> e = first;
                K k;
                do {
                    if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
                        old = e;
                        break;
                    }
                    ++binCount;
                } while ((e = e.next) != null);
            }
        }
        V oldValue = (old == null) ? null : old.value;
        V v = remappingFunction.apply(key, oldValue);
        if (old != null) {
            if (v != null) {
                old.value = v;
                afterNodeAccess(old);
            } else
                removeNode(hash, key, null, false, true);
        } else if (v != null) {
            if (t != null)
                t.putTreeVal(this, tab, hash, key, v);
            else {
                tab[i] = newNode(hash, key, v, first);
                if (binCount >= TREEIFY_THRESHOLD - 1)
                    treeifyBin(tab, hash);
            }
            ++modCount;
            ++size;
            afterNodeInsertion(true);
        }
        return v;
    }

    @Override
    public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
        if (value == null)
            throw new NullPointerException();
        if (remappingFunction == null)
            throw new NullPointerException();
        int hash = hash(key);
        Node<K, V>[] tab;
        Node<K, V> first;
        int n, i;
        int binCount = 0;
        TreeNode<K, V> t = null;
        Node<K, V> old = null;
        if (size > threshold || (tab = table) == null || (n = tab.length) == 0)
            n = (tab = resize()).length;
        if ((first = tab[i = (n - 1) & hash]) != null) {
            if (first instanceof TreeNode)
                old = (t = (TreeNode<K, V>) first).getTreeNode(hash, key);
            else {
                Node<K, V> e = first;
                K k;
                do {
                    if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) {
                        old = e;
                        break;
                    }
                    ++binCount;
                } while ((e = e.next) != null);
            }
        }
        if (old != null) {
            V v;
            if (old.value != null)
                v = remappingFunction.apply(old.value, value);
            else
                v = value;
            if (v != null) {
                old.value = v;
                afterNodeAccess(old);
            } else
                removeNode(hash, key, null, false, true);
            return v;
        }
        if (value != null) {
            if (t != null)
                t.putTreeVal(this, tab, hash, key, value);
            else {
                tab[i] = newNode(hash, key, value, first);
                if (binCount >= TREEIFY_THRESHOLD - 1)
                    treeifyBin(tab, hash);
            }
            ++modCount;
            ++size;
            afterNodeInsertion(true);
        }
        return value;
    }

    @Override
    public void forEach(BiConsumer<? super K, ? super V> action) {
        Node<K, V>[] tab;
        if (action == null)
            throw new NullPointerException();
        if (size > 0 && (tab = table) != null) {
            int mc = modCount;
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K, V> e = tab[i]; e != null; e = e.next)
                    action.accept(e.key, e.value);
            }
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }
    }

    @Override
    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
        Node<K, V>[] tab;
        if (function == null)
            throw new NullPointerException();
        if (size > 0 && (tab = table) != null) {
            int mc = modCount;
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K, V> e = tab[i]; e != null; e = e.next) {
                    e.value = function.apply(e.key, e.value);
                }
            }
            if (modCount != mc)
                throw new ConcurrentModificationException();
        }
    }

    /* ------------------------------------------------------------ */
    // Cloning and serialization

    /**
     * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and values
     * themselves are not cloned.
     *
     * @return a shallow copy of this map
     */
    @SuppressWarnings("unchecked")
    @Override
    public Object clone() {
        HashMap<K, V> result;
        try {
            result = (HashMap<K, V>) super.clone();
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError(e);
        }
        result.reinitialize();
        result.putMapEntries(this, false);
        return result;
    }

    // These methods are also used when serializing HashSets
    final float loadFactor() {
        return loadFactor;
    }

    final int capacity() {
        return (table != null) ? table.length : (threshold > 0) ? threshold : DEFAULT_INITIAL_CAPACITY;
    }

    /**
     * Save the state of the <tt>HashMap</tt> instance to a stream (i.e., serialize
     * it).
     *
     * @serialData The <i>capacity</i> of the HashMap (the length of the bucket
     *             array) is emitted (int), followed by the <i>size</i> (an int, the
     *             number of key-value mappings), followed by the key (Object) and
     *             value (Object) for each key-value mapping. The key-value mappings
     *             are emitted in no particular order.
     */
    private void writeObject(java.io.ObjectOutputStream s) throws IOException {
        int buckets = capacity();
        // Write out the threshold, loadfactor, and any hidden stuff
        s.defaultWriteObject();
        s.writeInt(buckets);
        s.writeInt(size);
        internalWriteEntries(s);
    }

    /**
     * Reconstitutes this map from a stream (that is, deserializes it).
     * 
     * @param s the stream
     * @throws ClassNotFoundException if the class of a serialized object could not
     *                                be found
     * @throws IOException            if an I/O error occurs
     */
    private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException {
        // Read in the threshold (ignored), loadfactor, and any hidden stuff
        s.defaultReadObject();
        reinitialize();
        if (loadFactor <= 0 || Float.isNaN(loadFactor))
            throw new InvalidObjectException("Illegal load factor: " + loadFactor);
        s.readInt(); // Read and ignore number of buckets
        int mappings = s.readInt(); // Read number of mappings (size)
        if (mappings < 0)
            throw new InvalidObjectException("Illegal mappings count: " + mappings);
        else if (mappings > 0) { // (if zero, use defaults)
            // Size the table using given load factor only if within
            // range of 0.25...4.0
            float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
            float fc = (float) mappings / lf + 1.0f;
            int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ? DEFAULT_INITIAL_CAPACITY
                    : (fc >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : tableSizeFor((int) fc));
            float ft = (float) cap * lf;
            threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ? (int) ft : Integer.MAX_VALUE);

            // Check Map.Entry[].class since it's the nearest public type to
            // what we're actually creating.
            SharedSecrets.getJavaOISAccess().checkArray(s, Map.Entry[].class, cap);
            @SuppressWarnings({ "rawtypes", "unchecked" })
            Node<K, V>[] tab = (Node<K, V>[]) new Node[cap];
            table = tab;

            // Read the keys and values, and put the mappings in the HashMap
            for (int i = 0; i < mappings; i++) {
                @SuppressWarnings("unchecked")
                K key = (K) s.readObject();
                @SuppressWarnings("unchecked")
                V value = (V) s.readObject();
                putVal(hash(key), key, value, false, false);
            }
        }
    }

    /* ------------------------------------------------------------ */
    // iterators

    abstract class HashIterator {
        Node<K, V> next; // next entry to return
        Node<K, V> current; // current entry
        int expectedModCount; // for fast-fail
        int index; // current slot

        HashIterator() {
            expectedModCount = modCount;
            Node<K, V>[] t = table;
            current = next = null;
            index = 0;
            if (t != null && size > 0) { // advance to first entry
                do {
                } while (index < t.length && (next = t[index++]) == null);
            }
        }

        public final boolean hasNext() {
            return next != null;
        }

        final Node<K, V> nextNode() {
            Node<K, V>[] t;
            Node<K, V> e = next;
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
            if (e == null)
                throw new NoSuchElementException();
            if ((next = (current = e).next) == null && (t = table) != null) {
                do {
                } while (index < t.length && (next = t[index++]) == null);
            }
            return e;
        }

        public final void remove() {
            Node<K, V> p = current;
            if (p == null)
                throw new IllegalStateException();
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
            current = null;
            K key = p.key;
            removeNode(hash(key), key, null, false, false);
            expectedModCount = modCount;
        }
    }

    final class KeyIterator extends HashIterator implements Iterator<K> {
        public final K next() {
            return nextNode().key;
        }
    }

    final class ValueIterator extends HashIterator implements Iterator<V> {
        public final V next() {
            return nextNode().value;
        }
    }

    final class EntryIterator extends HashIterator implements Iterator<Map.Entry<K, V>> {
        public final Map.Entry<K, V> next() {
            return nextNode();
        }
    }

    /* ------------------------------------------------------------ */
    // spliterators

    static class HashMapSpliterator<K, V> {
        final HashMap<K, V> map;
        Node<K, V> current; // current node
        int index; // current index, modified on advance/split
        int fence; // one past last index
        int est; // size estimate
        int expectedModCount; // for comodification checks

        HashMapSpliterator(HashMap<K, V> m, int origin, int fence, int est, int expectedModCount) {
            this.map = m;
            this.index = origin;
            this.fence = fence;
            this.est = est;
            this.expectedModCount = expectedModCount;
        }

        final int getFence() { // initialize fence and size on first use
            int hi;
            if ((hi = fence) < 0) {
                HashMap<K, V> m = map;
                est = m.size;
                expectedModCount = m.modCount;
                Node<K, V>[] tab = m.table;
                hi = fence = (tab == null) ? 0 : tab.length;
            }
            return hi;
        }

        public final long estimateSize() {
            getFence(); // force init
            return (long) est;
        }
    }

    static final class KeySpliterator<K, V> extends HashMapSpliterator<K, V> implements Spliterator<K> {
        KeySpliterator(HashMap<K, V> m, int origin, int fence, int est, int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public KeySpliterator<K, V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || current != null) ? null
                    : new KeySpliterator<>(map, lo, index = mid, est >>>= 1, expectedModCount);
        }

        public void forEachRemaining(Consumer<? super K> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap<K, V> m = map;
            Node<K, V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            } else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi && (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K, V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p.key);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        public boolean tryAdvance(Consumer<? super K> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K, V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        K k = current.key;
                        current = current.next;
                        action.accept(k);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }

        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) | Spliterator.DISTINCT;
        }
    }

    static final class ValueSpliterator<K, V> extends HashMapSpliterator<K, V> implements Spliterator<V> {
        ValueSpliterator(HashMap<K, V> m, int origin, int fence, int est, int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public ValueSpliterator<K, V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || current != null) ? null
                    : new ValueSpliterator<>(map, lo, index = mid, est >>>= 1, expectedModCount);
        }

        public void forEachRemaining(Consumer<? super V> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap<K, V> m = map;
            Node<K, V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            } else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi && (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K, V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p.value);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        public boolean tryAdvance(Consumer<? super V> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K, V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        V v = current.value;
                        current = current.next;
                        action.accept(v);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }

        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
        }
    }

    static final class EntrySpliterator<K, V> extends HashMapSpliterator<K, V> implements Spliterator<Map.Entry<K, V>> {
        EntrySpliterator(HashMap<K, V> m, int origin, int fence, int est, int expectedModCount) {
            super(m, origin, fence, est, expectedModCount);
        }

        public EntrySpliterator<K, V> trySplit() {
            int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid || current != null) ? null
                    : new EntrySpliterator<>(map, lo, index = mid, est >>>= 1, expectedModCount);
        }

        public void forEachRemaining(Consumer<? super Map.Entry<K, V>> action) {
            int i, hi, mc;
            if (action == null)
                throw new NullPointerException();
            HashMap<K, V> m = map;
            Node<K, V>[] tab = m.table;
            if ((hi = fence) < 0) {
                mc = expectedModCount = m.modCount;
                hi = fence = (tab == null) ? 0 : tab.length;
            } else
                mc = expectedModCount;
            if (tab != null && tab.length >= hi && (i = index) >= 0 && (i < (index = hi) || current != null)) {
                Node<K, V> p = current;
                current = null;
                do {
                    if (p == null)
                        p = tab[i++];
                    else {
                        action.accept(p);
                        p = p.next;
                    }
                } while (p != null || i < hi);
                if (m.modCount != mc)
                    throw new ConcurrentModificationException();
            }
        }

        public boolean tryAdvance(Consumer<? super Map.Entry<K, V>> action) {
            int hi;
            if (action == null)
                throw new NullPointerException();
            Node<K, V>[] tab = map.table;
            if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
                while (current != null || index < hi) {
                    if (current == null)
                        current = tab[index++];
                    else {
                        Node<K, V> e = current;
                        current = current.next;
                        action.accept(e);
                        if (map.modCount != expectedModCount)
                            throw new ConcurrentModificationException();
                        return true;
                    }
                }
            }
            return false;
        }

        public int characteristics() {
            return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) | Spliterator.DISTINCT;
        }
    }

    /* ------------------------------------------------------------ */
    // LinkedHashMap support

    /*
     * The following package-protected methods are designed to be overridden by
     * LinkedHashMap, but not by any other subclass. Nearly all other internal
     * methods are also package-protected but are declared final, so can be used by
     * LinkedHashMap, view classes, and HashSet.
     */

    // Create a regular (non-tree) node
    Node<K, V> newNode(int hash, K key, V value, Node<K, V> next) {
        return new Node<>(hash, key, value, next);
    }

    // For conversion from TreeNodes to plain nodes
    Node<K, V> replacementNode(Node<K, V> p, Node<K, V> next) {
        return new Node<>(p.hash, p.key, p.value, next);
    }

    // Create a tree bin node
    TreeNode<K, V> newTreeNode(int hash, K key, V value, Node<K, V> next) {
        return new TreeNode<>(hash, key, value, next);
    }

    // For treeifyBin
    TreeNode<K, V> replacementTreeNode(Node<K, V> p, Node<K, V> next) {
        return new TreeNode<>(p.hash, p.key, p.value, next);
    }

    /**
     * Reset to initial default state. Called by clone and readObject.
     */
    void reinitialize() {
        table = null;
        entrySet = null;
        keySet = null;
        values = null;
        modCount = 0;
        threshold = 0;
        size = 0;
    }

    // Callbacks to allow LinkedHashMap post-actions
    void afterNodeAccess(Node<K, V> p) {
    }

    void afterNodeInsertion(boolean evict) {
    }

    void afterNodeRemoval(Node<K, V> p) {
    }

    // Called only from writeObject, to ensure compatible ordering.
    void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
        Node<K, V>[] tab;
        if (size > 0 && (tab = table) != null) {
            for (int i = 0; i < tab.length; ++i) {
                for (Node<K, V> e = tab[i]; e != null; e = e.next) {
                    s.writeObject(e.key);
                    s.writeObject(e.value);
                }
            }
        }
    }

    /* ------------------------------------------------------------ */
    // Tree bins

    /**
     * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn extends Node)
     * so can be used as extension of either regular or linked node.
     */
    static final class TreeNode<K, V> extends LinkedHashMap.Entry<K, V> {
        TreeNode<K, V> parent; // red-black tree links
        TreeNode<K, V> left;
        TreeNode<K, V> right;
        TreeNode<K, V> prev; // needed to unlink next upon deletion
        boolean red;

        TreeNode(int hash, K key, V val, Node<K, V> next) {
            super(hash, key, val, next);
        }

        /**
         * Returns root of tree containing this node.
         */
        final TreeNode<K, V> root() {
            for (TreeNode<K, V> r = this, p;;) {
                if ((p = r.parent) == null)
                    return r;
                r = p;
            }
        }

        /**
         * Ensures that the given root is the first node of its bin.
         */
        static <K, V> void moveRootToFront(Node<K, V>[] tab, TreeNode<K, V> root) {
            int n;
            if (root != null && tab != null && (n = tab.length) > 0) {
                int index = (n - 1) & root.hash;
                TreeNode<K, V> first = (TreeNode<K, V>) tab[index];
                if (root != first) {
                    Node<K, V> rn;
                    tab[index] = root;
                    TreeNode<K, V> rp = root.prev;
                    if ((rn = root.next) != null)
                        ((TreeNode<K, V>) rn).prev = rp;
                    if (rp != null)
                        rp.next = rn;
                    if (first != null)
                        first.prev = root;
                    root.next = first;
                    root.prev = null;
                }
                assert checkInvariants(root);
            }
        }

        /**
         * Finds the node starting at root p with the given hash and key. The kc
         * argument caches comparableClassFor(key) upon first use comparing keys.
         */
        final TreeNode<K, V> find(int h, Object k, Class<?> kc) {
            TreeNode<K, V> p = this;
            do {
                int ph, dir;
                K pk;
                TreeNode<K, V> pl = p.left, pr = p.right, q;
                if ((ph = p.hash) > h)
                    p = pl;
                else if (ph < h)
                    p = pr;
                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                    return p;
                else if (pl == null)
                    p = pr;
                else if (pr == null)
                    p = pl;
                else if ((kc != null || (kc = comparableClassFor(k)) != null)
                        && (dir = compareComparables(kc, k, pk)) != 0)
                    p = (dir < 0) ? pl : pr;
                else if ((q = pr.find(h, k, kc)) != null)
                    return q;
                else
                    p = pl;
            } while (p != null);
            return null;
        }

        /**
         * Calls find for root node.
         */
        final TreeNode<K, V> getTreeNode(int h, Object k) {
            return ((parent != null) ? root() : this).find(h, k, null);
        }

        /**
         * Tie-breaking utility for ordering insertions when equal hashCodes and
         * non-comparable. We don't require a total order, just a consistent insertion
         * rule to maintain equivalence across rebalancings. Tie-breaking further than
         * necessary simplifies testing a bit.
         */
        static int tieBreakOrder(Object a, Object b) {
            int d;
            if (a == null || b == null || (d = a.getClass().getName().compareTo(b.getClass().getName())) == 0)
                d = (System.identityHashCode(a) <= System.identityHashCode(b) ? -1 : 1);
            return d;
        }

        /**
         * Forms tree of the nodes linked from this node.
         */
        final void treeify(Node<K, V>[] tab) {
            TreeNode<K, V> root = null;
            for (TreeNode<K, V> x = this, next; x != null; x = next) {
                next = (TreeNode<K, V>) x.next;
                x.left = x.right = null;
                if (root == null) {
                    x.parent = null;
                    x.red = false;
                    root = x;
                } else {
                    K k = x.key;
                    int h = x.hash;
                    Class<?> kc = null;
                    for (TreeNode<K, V> p = root;;) {
                        int dir, ph;
                        K pk = p.key;
                        if ((ph = p.hash) > h)
                            dir = -1;
                        else if (ph < h)
                            dir = 1;
                        else if ((kc == null && (kc = comparableClassFor(k)) == null)
                                || (dir = compareComparables(kc, k, pk)) == 0)
                            dir = tieBreakOrder(k, pk);

                        TreeNode<K, V> xp = p;
                        if ((p = (dir <= 0) ? p.left : p.right) == null) {
                            x.parent = xp;
                            if (dir <= 0)
                                xp.left = x;
                            else
                                xp.right = x;
                            root = balanceInsertion(root, x);
                            break;
                        }
                    }
                }
            }
            moveRootToFront(tab, root);
        }

        /**
         * Returns a list of non-TreeNodes replacing those linked from this node.
         */
        final Node<K, V> untreeify(HashMap<K, V> map) {
            Node<K, V> hd = null, tl = null;
            for (Node<K, V> q = this; q != null; q = q.next) {
                Node<K, V> p = map.replacementNode(q, null);
                if (tl == null)
                    hd = p;
                else
                    tl.next = p;
                tl = p;
            }
            return hd;
        }

        /**
         * Tree version of putVal.
         */
        final TreeNode<K, V> putTreeVal(HashMap<K, V> map, Node<K, V>[] tab, int h, K k, V v) {
            Class<?> kc = null;
            boolean searched = false;
            TreeNode<K, V> root = (parent != null) ? root() : this;
            for (TreeNode<K, V> p = root;;) {
                int dir, ph;
                K pk;
                if ((ph = p.hash) > h)
                    dir = -1;
                else if (ph < h)
                    dir = 1;
                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                    return p;
                else if ((kc == null && (kc = comparableClassFor(k)) == null)
                        || (dir = compareComparables(kc, k, pk)) == 0) {
                    if (!searched) {
                        TreeNode<K, V> q, ch;
                        searched = true;
                        if (((ch = p.left) != null && (q = ch.find(h, k, kc)) != null)
                                || ((ch = p.right) != null && (q = ch.find(h, k, kc)) != null))
                            return q;
                    }
                    dir = tieBreakOrder(k, pk);
                }

                TreeNode<K, V> xp = p;
                if ((p = (dir <= 0) ? p.left : p.right) == null) {
                    Node<K, V> xpn = xp.next;
                    TreeNode<K, V> x = map.newTreeNode(h, k, v, xpn);
                    if (dir <= 0)
                        xp.left = x;
                    else
                        xp.right = x;
                    xp.next = x;
                    x.parent = x.prev = xp;
                    if (xpn != null)
                        ((TreeNode<K, V>) xpn).prev = x;
                    moveRootToFront(tab, balanceInsertion(root, x));
                    return null;
                }
            }
        }

        /**
         * Removes the given node, that must be present before this call. This is
         * messier than typical red-black deletion code because we cannot swap the
         * contents of an interior node with a leaf successor that is pinned by "next"
         * pointers that are accessible independently during traversal. So instead we
         * swap the tree linkages. If the current tree appears to have too few nodes,
         * the bin is converted back to a plain bin. (The test triggers somewhere
         * between 2 and 6 nodes, depending on tree structure).
         */
        final void removeTreeNode(HashMap<K, V> map, Node<K, V>[] tab, boolean movable) {
            int n;
            if (tab == null || (n = tab.length) == 0)
                return;
            int index = (n - 1) & hash;
            TreeNode<K, V> first = (TreeNode<K, V>) tab[index], root = first, rl;
            TreeNode<K, V> succ = (TreeNode<K, V>) next, pred = prev;
            if (pred == null)
                tab[index] = first = succ;
            else
                pred.next = succ;
            if (succ != null)
                succ.prev = pred;
            if (first == null)
                return;
            if (root.parent != null)
                root = root.root();
            if (root == null || (movable && (root.right == null || (rl = root.left) == null || rl.left == null))) {
                tab[index] = first.untreeify(map); // too small
                return;
            }
            TreeNode<K, V> p = this, pl = left, pr = right, replacement;
            if (pl != null && pr != null) {
                TreeNode<K, V> s = pr, sl;
                while ((sl = s.left) != null) // find successor
                    s = sl;
                boolean c = s.red;
                s.red = p.red;
                p.red = c; // swap colors
                TreeNode<K, V> sr = s.right;
                TreeNode<K, V> pp = p.parent;
                if (s == pr) { // p was s's direct parent
                    p.parent = s;
                    s.right = p;
                } else {
                    TreeNode<K, V> sp = s.parent;
                    if ((p.parent = sp) != null) {
                        if (s == sp.left)
                            sp.left = p;
                        else
                            sp.right = p;
                    }
                    if ((s.right = pr) != null)
                        pr.parent = s;
                }
                p.left = null;
                if ((p.right = sr) != null)
                    sr.parent = p;
                if ((s.left = pl) != null)
                    pl.parent = s;
                if ((s.parent = pp) == null)
                    root = s;
                else if (p == pp.left)
                    pp.left = s;
                else
                    pp.right = s;
                if (sr != null)
                    replacement = sr;
                else
                    replacement = p;
            } else if (pl != null)
                replacement = pl;
            else if (pr != null)
                replacement = pr;
            else
                replacement = p;
            if (replacement != p) {
                TreeNode<K, V> pp = replacement.parent = p.parent;
                if (pp == null)
                    root = replacement;
                else if (p == pp.left)
                    pp.left = replacement;
                else
                    pp.right = replacement;
                p.left = p.right = p.parent = null;
            }

            TreeNode<K, V> r = p.red ? root : balanceDeletion(root, replacement);

            if (replacement == p) { // detach
                TreeNode<K, V> pp = p.parent;
                p.parent = null;
                if (pp != null) {
                    if (p == pp.left)
                        pp.left = null;
                    else if (p == pp.right)
                        pp.right = null;
                }
            }
            if (movable)
                moveRootToFront(tab, r);
        }

        /**
         * Splits nodes in a tree bin into lower and upper tree bins, or untreeifies if
         * now too small. Called only from resize; see above discussion about split bits
         * and indices.
         *
         * @param map   the map
         * @param tab   the table for recording bin heads
         * @param index the index of the table being split
         * @param bit   the bit of hash to split on
         */
        final void split(HashMap<K, V> map, Node<K, V>[] tab, int index, int bit) {
            TreeNode<K, V> b = this;
            // Relink into lo and hi lists, preserving order
            TreeNode<K, V> loHead = null, loTail = null;
            TreeNode<K, V> hiHead = null, hiTail = null;
            int lc = 0, hc = 0;
            for (TreeNode<K, V> e = b, next; e != null; e = next) {
                next = (TreeNode<K, V>) e.next;
                e.next = null;
                if ((e.hash & bit) == 0) {
                    if ((e.prev = loTail) == null)
                        loHead = e;
                    else
                        loTail.next = e;
                    loTail = e;
                    ++lc;
                } else {
                    if ((e.prev = hiTail) == null)
                        hiHead = e;
                    else
                        hiTail.next = e;
                    hiTail = e;
                    ++hc;
                }
            }

            if (loHead != null) {
                if (lc <= UNTREEIFY_THRESHOLD)
                    tab[index] = loHead.untreeify(map);
                else {
                    tab[index] = loHead;
                    if (hiHead != null) // (else is already treeified)
                        loHead.treeify(tab);
                }
            }
            if (hiHead != null) {
                if (hc <= UNTREEIFY_THRESHOLD)
                    tab[index + bit] = hiHead.untreeify(map);
                else {
                    tab[index + bit] = hiHead;
                    if (loHead != null)
                        hiHead.treeify(tab);
                }
            }
        }

        /* ------------------------------------------------------------ */
        // Red-black tree methods, all adapted from CLR

        static <K, V> TreeNode<K, V> rotateLeft(TreeNode<K, V> root, TreeNode<K, V> p) {
            TreeNode<K, V> r, pp, rl;
            if (p != null && (r = p.right) != null) {
                if ((rl = p.right = r.left) != null)
                    rl.parent = p;
                if ((pp = r.parent = p.parent) == null)
                    (root = r).red = false;
                else if (pp.left == p)
                    pp.left = r;
                else
                    pp.right = r;
                r.left = p;
                p.parent = r;
            }
            return root;
        }

        static <K, V> TreeNode<K, V> rotateRight(TreeNode<K, V> root, TreeNode<K, V> p) {
            TreeNode<K, V> l, pp, lr;
            if (p != null && (l = p.left) != null) {
                if ((lr = p.left = l.right) != null)
                    lr.parent = p;
                if ((pp = l.parent = p.parent) == null)
                    (root = l).red = false;
                else if (pp.right == p)
                    pp.right = l;
                else
                    pp.left = l;
                l.right = p;
                p.parent = l;
            }
            return root;
        }

        static <K, V> TreeNode<K, V> balanceInsertion(TreeNode<K, V> root, TreeNode<K, V> x) {
            x.red = true;
            for (TreeNode<K, V> xp, xpp, xppl, xppr;;) {
                if ((xp = x.parent) == null) {
                    x.red = false;
                    return x;
                } else if (!xp.red || (xpp = xp.parent) == null)
                    return root;
                if (xp == (xppl = xpp.left)) {
                    if ((xppr = xpp.right) != null && xppr.red) {
                        xppr.red = false;
                        xp.red = false;
                        xpp.red = true;
                        x = xpp;
                    } else {
                        if (x == xp.right) {
                            root = rotateLeft(root, x = xp);
                            xpp = (xp = x.parent) == null ? null : xp.parent;
                        }
                        if (xp != null) {
                            xp.red = false;
                            if (xpp != null) {
                                xpp.red = true;
                                root = rotateRight(root, xpp);
                            }
                        }
                    }
                } else {
                    if (xppl != null && xppl.red) {
                        xppl.red = false;
                        xp.red = false;
                        xpp.red = true;
                        x = xpp;
                    } else {
                        if (x == xp.left) {
                            root = rotateRight(root, x = xp);
                            xpp = (xp = x.parent) == null ? null : xp.parent;
                        }
                        if (xp != null) {
                            xp.red = false;
                            if (xpp != null) {
                                xpp.red = true;
                                root = rotateLeft(root, xpp);
                            }
                        }
                    }
                }
            }
        }

        static <K, V> TreeNode<K, V> balanceDeletion(TreeNode<K, V> root, TreeNode<K, V> x) {
            for (TreeNode<K, V> xp, xpl, xpr;;) {
                if (x == null || x == root)
                    return root;
                else if ((xp = x.parent) == null) {
                    x.red = false;
                    return x;
                } else if (x.red) {
                    x.red = false;
                    return root;
                } else if ((xpl = xp.left) == x) {
                    if ((xpr = xp.right) != null && xpr.red) {
                        xpr.red = false;
                        xp.red = true;
                        root = rotateLeft(root, xp);
                        xpr = (xp = x.parent) == null ? null : xp.right;
                    }
                    if (xpr == null)
                        x = xp;
                    else {
                        TreeNode<K, V> sl = xpr.left, sr = xpr.right;
                        if ((sr == null || !sr.red) && (sl == null || !sl.red)) {
                            xpr.red = true;
                            x = xp;
                        } else {
                            if (sr == null || !sr.red) {
                                if (sl != null)
                                    sl.red = false;
                                xpr.red = true;
                                root = rotateRight(root, xpr);
                                xpr = (xp = x.parent) == null ? null : xp.right;
                            }
                            if (xpr != null) {
                                xpr.red = (xp == null) ? false : xp.red;
                                if ((sr = xpr.right) != null)
                                    sr.red = false;
                            }
                            if (xp != null) {
                                xp.red = false;
                                root = rotateLeft(root, xp);
                            }
                            x = root;
                        }
                    }
                } else { // symmetric
                    if (xpl != null && xpl.red) {
                        xpl.red = false;
                        xp.red = true;
                        root = rotateRight(root, xp);
                        xpl = (xp = x.parent) == null ? null : xp.left;
                    }
                    if (xpl == null)
                        x = xp;
                    else {
                        TreeNode<K, V> sl = xpl.left, sr = xpl.right;
                        if ((sl == null || !sl.red) && (sr == null || !sr.red)) {
                            xpl.red = true;
                            x = xp;
                        } else {
                            if (sl == null || !sl.red) {
                                if (sr != null)
                                    sr.red = false;
                                xpl.red = true;
                                root = rotateLeft(root, xpl);
                                xpl = (xp = x.parent) == null ? null : xp.left;
                            }
                            if (xpl != null) {
                                xpl.red = (xp == null) ? false : xp.red;
                                if ((sl = xpl.left) != null)
                                    sl.red = false;
                            }
                            if (xp != null) {
                                xp.red = false;
                                root = rotateRight(root, xp);
                            }
                            x = root;
                        }
                    }
                }
            }
        }

        /**
         * Recursive invariant check
         */
        static <K, V> boolean checkInvariants(TreeNode<K, V> t) {
            TreeNode<K, V> tp = t.parent, tl = t.left, tr = t.right, tb = t.prev, tn = (TreeNode<K, V>) t.next;
            if (tb != null && tb.next != t)
                return false;
            if (tn != null && tn.prev != t)
                return false;
            if (tp != null && t != tp.left && t != tp.right)
                return false;
            if (tl != null && (tl.parent != t || tl.hash > t.hash))
                return false;
            if (tr != null && (tr.parent != t || tr.hash < t.hash))
                return false;
            if (t.red && tl != null && tl.red && tr != null && tr.red)
                return false;
            if (tl != null && !checkInvariants(tl))
                return false;
            if (tr != null && !checkInvariants(tr))
                return false;
            return true;
        }
    }

}
